Liquid crystal display device and fabricating method thereof

ABSTRACT

A liquid crystal display device comprising a first substrate, a second substrate, a liquid crystal layer and a shading film is provided. The first substrate includes a display region and a non-display region. The liquid crystal layer is sandwiched between the first substrate and the second substrate. The shading film is located between the first substrate and the liquid crystal layer covering the non-display region. With the shading film covering the entire non-display region, the problem of light leakage from the edge of the display device is resolved.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to a display device and fabricating methodthereof. More particularly, the present invention relates to a liquidcrystal display device and fabricating method thereof.

2. Description of the Related Art

With big advance in electronic technologies, digital video products orimaging devices has become one of the most common electronic gadgets inour daily life. Among various video products and imaging devices,display devices inarguably occupy a central position because a user mustextract information from a display device, or in the case of performinga real-time control, receive real-time data from a display device.

To fit the lifestyle of modern day people, the size and weight of videoand imaging products must be reduced as much as possible. Althoughcathode ray tubes (CRT) still has some advantages, bulkiness and volumeare the two major setbacks that reduce its popularity in the future.With breakthroughs in photo-electronic and semiconductor fabricationtechnologies, panel type displays such as the liquid crystal displaysare starting to replace the conventional CRT because of its lowoperating voltage, radiation free operation and light-weight andstreamline body. In fact, researches in liquid crystal display and otherflat panel displays such as plasma display panel and electro-luminancedisplays have dominated the field in recent years due to its potentialas a mainstream product in the market.

In general, a thin film transistor (TFT) liquid crystal displaycomprises a thin film transistor array substrate, a color filtersubstrate and a liquid crystal layer. FIG. 1 is a schematiccross-sectional view of a conventional liquid crystal display panel. Theliquid crystal display panel in FIG. 1 comprises a color filtersubstrate 100, a thin film transistor array substrate 102, a sealant 104and a liquid crystal layer 106. The liquid crystal layer 106 is enclosedwithin the space bounded by the color filter substrate 100, the thinfilm transistor array substrate 102 and the sealant 104. The colorfilter substrate 100 further comprises a color filter 113 and a blackmatrix 114. Furthermore, the thin film transistor array substrate 102comprises a display region 108 and a non-display region 110. Thenon-display region 110 has a plurality of lead lines 112 serving asdrivers for operating the display device.

To form the liquid crystal layer 106, the sealant 104 is placed betweenthe substrates 100 and 102 to form an enclosed space. Thereafter, asmall quantity of liquid crystal is gradually filled into the spacebetween the color filter substrate 100 and the thin film transistorarray substrate 102 under a capillary effect due to the presence of anexternal atmospheric pressure. Because the injection speed of liquidcrystal under capillary effect is slow, other injection techniques suchas the one-drop fill (ODF) process is deployed. In the one-drop fillprocess, a layer of UV sealant is coated on the thin film transistorarray substrate 102 (or the color substrate 100) to form a sealant 104.Each drop of liquid crystal is dropped inside the area enclosed by thesealant 104. Thereafter, the color filter substrate 100 (or the thinfilm transistor array substrate 102) is placed over the sealant 104. Thesealant 104 is illuminated with UV light so that the sealant 104 hardensso that the sealant 104 bonds the color filter substrate 100 and thethin film transistor array substrate 102 together.

Using the ODF technique, time for injecting liquid crystal into a liquidcrystal display panel is reduced considerably. For example, only 2 hoursare required to fill a 30 inches panel using the ODF technique. If thesame display panel is filled using the capillary injection technique,roughly five days are required. Hence, production time is shortenedconsiderably. Furthermore, ODF technique requires only 40% of the liquidcrystal needed in a capillary injection process. However, care must beexecuted to prevent any contamination of the liquid crystal by thesealant that may lead to liquid crystal display problems. In general,the black matrix (BM) 114 on the color filter substrate 100 has to movea definite distance toward the central area of the panel. With the blackmatrix (BM) 114 moved from the edges, a strip of area 116 adjacent tothe edge is no longer covered with any barrier. Since the gap betweenlead lines 112 in the non-display region 110 has no barrier, light caneasily leak from the edge of the display panel.

SUMMARY OF INVENTION

Accordingly, one objective of the present invention is to provide aliquid crystal display device capable of minimizing the amount of lightleakage from the edges of the display device.

Another objective of the present invention is to provide a method offabricating a liquid crystal display device capable of minimizing theamount of light leakage from the edges of the display device withoutincreasing the number of processing steps.

To achieve these and other advantages and in accordance with the purposeof the invention, as embodied and broadly described herein, the presentinvention provides a liquid crystal display device. The display devicecomprises a first substrate, a second substrate, a liquid crystal layerand a first shading film. The first substrate includes a display regionand a non-display region positioned around the periphery of the firstsubstrate. The liquid crystal layer is sandwiched between the firstsubstrate and the second substrate. The first shading film is setbetween the first substrate and the liquid crystal layer within thenon-display region. Furthermore, the first substrate further includes atleast a thin film transistor with at least a gate and a source/drain.

The present invention also provides a method of fabricating a liquidcrystal device. First, a first substrate is provided. The firstsubstrate has a display region and a non-display region positionedaround the periphery of the display region. Thereafter, at least a thinfilm transistor is formed within the display region. The method offorming the thin film transistor includes forming a gate over the firstsubstrate, forming an insulating layer over the first substrate to coverthe gate, forming a channel layer over the insulating layer above thegate and forming a source source/drain region over the channel layer.The process of fabricating the thin film transistor further includesforming a first shading film within the non-display region. The firstshading film is formed together with either the gate or thesource/drain. Thereafter, a second substrate is provided. A sealant isformed on the first substrate or the second substrate. A liquid crystallayer is formed on the substrate surface with the sealant. The firstsubstrate and the second substrate are bonded together and then thesealant is illuminated.

In the aforementioned liquid crystal display device and fabricatingmethod, the first shading film is set over the non-display region insuch a way that the entire non-display region is covered.

The aforementioned liquid crystal display device and fabricating methodthereof further includes forming a plurality of lead lines within thenon-display region. The lead lines and the gate are fabricated togetheror the lead lines and the source/drain are fabricated together. When thelead lines and the gate are fabricated together, the first shading filmand the source/drain are formed at the same time in a position above thegap between neighboring lead lines within the non-display region.Alternatively, an additional second shading film is set up within thenon-display region. The second shading film and the gate are formedtogether and positioned between neighboring lead lines. Furthermore, thesecond shading film is electrically isolated from its neighboring leadlines. The first shading film is set over the gap between the secondshading film and an adjacent lead line.

When the lead lines and the source/drain are formed at the same time,the first shading film and the gate are fabricated together andpositioned underneath the gap between neighboring lead lines within thenon-display region. Alternatively, an additional second shading film isset within the non-display region. The second shading film and thesource/drain are formed together and positioned between neighboring leadlines. Furthermore, the second shading film is electrically isolatedfrom its neighboring lead lines. The first shading film is setunderneath the gap between the second shading film and an adjacent leadline.

In the present invention, an additional shading film is set between theliquid crystal layer and the first substrate of the liquid crystaldisplay device. The shading film essentially blocks out any light tryingto escape through the non-display region near the edge of the displaydevice.

In the process of fabricating the liquid crystal display device, thefirst shading film is formed within the non-display region close to theedge of the substrate together with the source/drain (or the gate).Hence, there is no need to introduce extra processing steps just toprevent any light leakage from the edge of the display device.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a schematic cross-sectional view of a conventional liquidcrystal display panel.

FIG. 2 is a schematic cross-sectional view of a liquid crystal displaydevice according to a first preferred embodiment of this invention.

FIG. 3 is a schematic cross-sectional view of a liquid crystal displaydevice according to a second preferred embodiment of this invention.

FIG. 4 is a schematic cross-sectional view of a liquid crystal displaydevice according to a third preferred embodiment of this invention.

FIGS. 5A through 5D are schematic cross-sectional views showing thesteps for fabricating a liquid crystal display device according to onepreferred embodiment of this invention.

FIG. 6 is a schematic cross-sectional view of a liquid crystal displaydevice according to a fourth preferred embodiment of this invention.

FIG. 7 is a schematic cross-sectional view of a liquid crystal displaydevice according to a fifth preferred embodiment of this invention.

FIG. 8 is a schematic cross-sectional view of a liquid crystal displaydevice according to a sixth preferred embodiment of this invention.

DETAILED DESCRIPTION

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

FIG. 2 is a schematic cross-sectional view of a liquid crystal displaydevice according to a first preferred embodiment of this invention. Theliquid crystal display device comprises a first substrate 200, a secondsubstrate 202, a liquid crystal layer 204 and a first shading film 222.The first substrate 200 is a color filter substrate with a color filter208 thereon, for example. The color filter 208 further comprises aplurality of red (R) filter films 210, green (G) filter films 210 orblue (B) filter films 210. The color filter 208 are organized into amosaic, a delta or a stripe pattern. In addition, a net-like blackmatrix 212 is also formed in the space between the color filter 208. Aplurality of other film layers (not shown) may also be formed over thecolor filter 208 such as a passivation film 226, a metal electrode filmand an alignment film. The passivation film 226 can protect the colorfilter 208, and make it planar. Furthermore, the electrode film may befabricated using indium-tin-oxide (ITO) or equivalent materials. Thealignment film serves as a guide to orient any liquid crystal moleculeson the film to a pre-defined direction (alignment) so that the liquidcrystal molecules are pre-tilted. The other surface of the firstsubstrate 200 may include a polarizing plate (not shown) that provides adisplay function.

The second substrate 202 is thin film transistor array substrate, forexample. The second substrate 202 comprises a display region 214 and anon-display region 216. The display region 214 includes at least a thinfilm transistor 217 (having a gate 302, a source 306 a and a drain 306b). The non-display region 216 includes a plurality of lead lines 218thereon. Furthermore, an insulation layer 220 that joins with the gateinsulation layer of the thin film transistor 217 is also formed over thelead lines 218.

The first shading film 222 is set between the second substrate 202 andthe liquid crystal layer 204 within the non-display region 216. Thefirst shading film 222 is formed using a substance selected from a groupof conductive and non-transparent materials, for example.

It is to be noted that the first shading film 222 and the source 304a/drain 304 b (306 a/306 b) in this embodiment are fabricated using thesame film material. In other words, the first shading film 222 and thesource 306 a/drain 306 b are formed together in the same step.Similarly, the lead lines 218 and the gate 302 are fabricated using thesame film material. In an alternative embodiment, the first shading film222 and the gate 302 are fabricated using the same film material. Inother words, the first shading film 222 and the gate 302 are formedtogether in the same step. In this case, the lead lines 218 and thesource 306 a/drain 306 b are also fabricated using the same filmmaterial.

The first shading film 222 is set on the non-display region 216 so thatthe first shading film 222 covers the non-display region 216 completely(as shown in FIG. 2) or lies underneath the non-display region 216 (asshown in FIG. 6).

In another embodiment of this invention, the first shading film 222 isset over (or underneath) the gaps between neighboring lead lines 218within the non-display region 216 (as shown in FIG. 3 and FIG. 7). Withthis structural setup, the first shading film 222 is prevented fromforming a short circuit with neighboring lead lines 218 and the firstshading film 222 due to some imperfection in the process of fabricatingthe first shading film 222.

In another embodiment, a second shading film 224 is formed within thenon-display region 216. The second shading film 224 is set betweenneighboring lead lines 218 and electrically isolated from them.Furthermore, the first shading film 222 is positioned over (orunderneath) the gap between the second shading film 224 and the leadline 218 (as shown in FIG. 4 and FIG. 8). With this structural setup,the first shading film 222 is prevented from forming a short circuitwith neighboring lead lines 218 and the first shading film 222 due tosome imperfection in the process of fabricating the first shading film222.

In addition, the sealant 206 is set between the first substrate 200 andthe second substrate 202 to form an interior space for holding theliquid crystal molecules. The sealant 206 is fabricated from an UVphotosensitive material, for example.

Obviously, other film layers may also be formed over the secondsubstrate 202. For example, a passivation film 226, an electrode film(not shown) and an alignment film (not shown) are sequentially formedover the second substrate 202. Furthermore, a polarizing plate (notshown) may also be formed on the other surface of the second substrate202.

Accordingly, an additional shading film is formed between the liquidcrystal layer and the second substrate 202. The shading film is set insuch a way that the non-display region is completely covered by theshading film or the shading film is set over the gap between neighboringlead lines. Alternatively, a shading film is first set in the gapbetween neighboring lead lines and then another shading film is set overthe gap between the first shading film and the lead lines. Hence, thisinvention provides an effective means of preventing light leakage fromthe edge of the display device (the non-display region).

FIGS. 5A through 5D are schematic cross-sectional views showing thesteps for fabricating a liquid crystal display device according to onepreferred embodiment of this invention. In particular, FIGS. 5A through5C illustrates the process of fabricating a substrate 202. As shown inFIG. 5A, a substrate 300 is provided. The substrate 300 includes adisplay region 214 and a non-display region 216 positioned around theperiphery of the substrate 300. The substrate 300 is a glass substrateor a transparent plastic substrate, for example. Thereafter, a metalliclayer having a thickness of several thousand angstroms is formed overthe substrate 300 and then patterned to form at least a gate 302 withinthe display region 214 and a plurality of lead lines 218 within thenon-display region 216. The metallic layer is formed, for example, byperforming a sputtering. The lead lines 218 subsequently serve asdriving lines for the device. Next, an insulation layer 220 is formedover the substrate 300 globally to cover the gate 302 and the lead lines218. The insulation layer 220 is, for example, a silicon nitride layeror a silicon oxide layer formed by performing a plasma chemical vapordeposition.

As shown in FIG. 5B, a channel material layer (not shown) is formed overthe insulation layer 220 and then patterned to form a channel layer 304.The channel layer 304 is positioned over the insulation layer 220 abovethe gate 302 and is fabricated using amorphous silicon, for example.

As shown in FIG. 5C, another metallic layer (not shown) is formed overthe substrate 300 and then patterned to form a source 306 a/drain 306 band a first shading film 222. The first shading film 222 is fabricatedusing a substance selected from a group of conductive andnon-transparent materials. The gate 302, the channel layer 304 and thesource 306 a/306 b together form a thin film transistor 217. It is to benoted that in one embodiment of this invention, the first shading film222 covers the entire non-display region 216 (as shown in FIG. 2 andFIG. 5C). In another embodiment, the first shading film 222 is formedover the gap between neighboring lead lines 218 (as shown in FIG. 3) sothat a short circuit between the first shading film 222 and the leadlines 218 due to manufacturing defect is prevented.

In another embodiment, in the process of forming the lead lines 218, asecond shading film 224 is also patterned out in the gap betweenneighboring lead lines 218. The second shading film 224 is electricallyisolated from neighboring lead lines 218 (as shown in FIG. 4) and isfabricated using a substance selected from a group of conductive andnon-transparent materials. Thereafter, in the process of patterning outthe source 306 a/drain 306 b, the first shading film 222 is alsosimultaneously patterned so that the patterned first shading film 222 islocated above the gap between the second shading film 224 andneighboring lead lines 218. Consequently, the probability of having ashort circuit between the first shading film 222 and the lead lines 218due to an imperfection in the manufacturing process is minimized.

Obviously, other film layers may also be formed over the substrate 300.For example, a passivation film 226, an electrode film (not shown) andan alignment film (not shown) are sequentially formed over the substrate202. Furthermore, a polarizing plate (not shown) may also be formed onthe other surface of the substrate 300.

As shown in FIG. 5D, a color filter substrate 200 is provided. The colorfilter substrate 200 has at least a black matrix 212 and a color filter210 thereon. A sealant 206 is coated on the substrate 300 or on thecolor filter substrate 200 just outside the black matrix 212 to form anenclosed area. Thereafter, liquid crystal 204 is dropped into the areaenclosed by the UV sealant 206 and then the thin film transistorsubstrate 300 and the color filter substrate 200 are pressed together.Finally, ultraviolet light 308 is shone to harden the sealant 206 andbind the two substrates (200 and 300) together.

In the aforementioned embodiment, the first shading film 222 and thesource 306 a/drain 306 b are formed together in the same step. However,if the lead lines 218 and the source 306 a/drain 306 b are formedtogether in the same step, the first shading film 222 and the gate 302can be formed together in the same step. When the first shading film 222and the gate 302 are formed together in the same step, the first shadingfilm 222 may lie underneath the non-display region 216 (as shown in FIG.6) in one embodiment. Alternatively, the first shading film 222 may lieunderneath the gap between neighboring lead lines 218 (as shown in FIG.7).

In another embodiment, the second shading film 224 is formed in the gapbetween neighboring lead lines 218 and are formed together in the samestep. However, the second shading film 224 is electrically isolated fromneighboring lead lines 218 (as shown in FIG. 8). The first shading film222 is formed underneath the gap between the second shading film 224 andthe lead lines 218. With this setup, a short circuit between the firstshading film 222 and the lead lines 218 can be prevented.

According to the method of fabricating liquid crystal display device inthis invention, a shading film is formed within the non-display regionof a substrate near the edge of the substrate in the process offabricating the source/drain (or gate). Alternatively, a second shadingfilm the gate (or source/drain) are formed in the same step. Hence,there is no need to introduce an extra step in the fabricating processjust to prevent the leakage of light from the edges of the displaydevice.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. A liquid crystal display device, comprising: a first substrate havinga display region and a non-display region around the periphery of thedisplay region; a second substrate; a liquid crystal layer sandwichedbetween the first substrate and the second substrate; a first shadingfilm disposed between the first substrate and the liquid crystal layerwithin the non-display region of the first substrate; a plurality oflead lines disposed over the non-display region of the first substrate;and a second shading film disposed over the gap between neighboring leadlines within the non-display region, wherein the second shading film iselectrically isolated from the neighboring lead lines, and the firstshading film is disposed over the gap between the second shading filmand neighboring lead lines, such that the first shading film, the secondshading film and the lead lines are located at different height levelsand electrically isolated from one another.
 2. The liquid crystaldisplay device of claim 1, wherein the first shading film covers overthe non-display region.
 3. The liquid crystal display device of claim 1,wherein the first shading film is positioned over the gap betweenneighboring lead lines within the non-display region and the firstshading film and the lead lines are electrically isolated from eachother and located at different height levels.
 4. The liquid crystaldisplay device of claim 1, wherein the first substrate includes at leasta thin film transistor with a gate, a source and a drain.
 5. The liquidcrystal display device of claim 4, wherein the first shading film andthe source/drain are fabricated using the same film material.
 6. Theliquid crystal display device of claim 1, further comprising a blackmatrix layer set between the second substrate and the liquid crystallayer.
 7. The liquid crystal display device of claim 4, wherein thefirst shading film and the gate are fabricated using the same filmmaterial.